Proof: Let x2=u3,y2=v3,z2=w3, then equation (36) can be rewritten as
vw+2u2vw+wu+2v2wu+uv+2w2uv⩾1,
where u,v,w are positive real numbers, and satisfy uvw=4.
Since
=vw+2u2vw+wu+2v2wu+uv+2w2uv−1(2u2+vw)(2v2+wu)(2w2+uv)uvw(u+v+w)[(v−w)2+(w−u)2+(u−v)2]⩾0
Therefore, equation (37) holds, which means equation (36) holds.